This invention relates generally to distributed computing systems, and more particularly to a method and apparatus for performing event notification in a database having a distributed web cluster.
Modern computerized search systems can contain vast amounts of data. In order to be useful, they must return search results to a user in a reasonable amount of time. One application for computerized search systems is that of finding geographic entities such as an address, street, area, point, businesses, or list of cities that are located near a given starting point. For example, with a system containing a database of homes and businesses with corresponding addresses or geographical locations within a city, a user may want to locate banks, automated teller machines (ATMs), or restaurants which are close to a specific address or business within the city. Because the user may be waiting for the results of the search in real-time, the search results must be returned very quickly. In addition, the results should preferably be presented in an ordered format according to the usefulness to the user. For example, some businesses might have a sale or special offering which should be presented to the user before other businesses which do not have a sale or special.
To improve the access speed to information through public data networks such as the Internet, database information may be copied or xe2x80x9cmirroredxe2x80x9d across one or more physically distributed servers, known as web clusters. The servers may be widely separated geographically and may contain multiple independent data paths which are separated from those of other servers.
With a distributed data network having multiple data servers, there is a problem in updating and maintaining consistent information on all of the servers. For example, if new information is uploaded to one server, the information must also be distributed to and synchronized with the other mirror servers within the network. In some prior art systems, update information is broadcast to the mirror servers once a day. While this approach may be acceptable for information which does not generally change very rapidly, such as static links to web sites, it leads to server inconsistencies and unacceptable delays for time-critical information such as stock quotes or news reports.
Therefore, there is a need for a way to update time-critical information in a database having multiple servers in a distributed web cluster.
The present invention provides a method and apparatus for performing event notification in a system having a distributed web cluster. A change of state is provided to the system. A state change table is updated in the system with the provided change of state. The change of state is propagated from the state change table to the web cluster, through polling, broadcast, or other methods. The web cluster is synchronized to reflect the state change.